The lambda symbol seems to be one of the most controversial of symbols in regard to its meaning. There are several differing opinions as to why the lambda was chosen as a gay symbol and what it really means. However, most sources agree on a few things:
The lambda was first chosen as a gay symbol when it was adopted in 1970 by the New York Gay Activists Alliance. It became the symbol of their growing movement of gay liberation. In 1974, the lambda was subsequently adopted by the International Gay Rights Congress held in Edinburgh, Scotland. As their symbol for lesbian and gay rights, the lambda became internationally popular.
But where history ends, speculation begins. No one seems to have a definitive answer why the lambda was originally chosen as a gay symbol. Some suggest that it is simply the Greek lower-case letter l for liberation. Others disagree, citing the use of lambda in physics to denote energy (the energy we have when we work in concert) or wavelength (are gays and lesbians on a different wavelength?). Lambda may also denote the synergy of the gay movement, the idea that the whole is greater than the sum of its parts. The lambda also may represent scales and balance, and the constant force that keeps opposing sides from overcoming each other — the hook at the bottom of the right leg signifies the action needed to reach and maintain balance. The ancient Greek Spartans regarded the lambda to mean unity, while the Romans considered it «the light of knowledge shed into the darkness of ignorance».
Whatever the exact meaning and origin, the lambda originally embodied a fairly militant connotation. Today, the symbol generally denotes lesbian’s and gay men’s concerns together. Although the lambda was never intended to be linked to any specific gender or orientation such as other symbols may be, historically this is not so: In the early 1970’s the Los Angeles gay community created a flag with a lavender lambda on a simple white background. They hoped the flag would catch on to other cities, but their hopes were denied because some saw the lambda as a male symbol only.